Embodiments of the present disclosure provide an uplink control information transmission method, a terminal device, a base station, and a system. The transmission method includes the following steps: First, the terminal device determines an information bit sequence of to-be-transmitted uplink control information. Then, the terminal device determines a first sequence according to the information bit sequence, where the first sequence is a linear-phase complex exponential sequence. Finally, the terminal device sends the to-be-transmitted uplink control information to the base station by using an uplink control channel, where the uplink control channel occupies N symbols, N is a positive integer, a signal carried on a symbol l of the N symbols is directly proportional to a product of the first sequence and a second sequence, and the second sequence is a cyclic shift sequence.